Process of preparing an iron catalyst promoted with an alkali metal fluoborate



9 man may 24,1949

2.471.130 I J I PROCESS OF PREPARING AN IRON CATA- LYST PROMOTED WITH AN ALKALI METAL' FLUOBORATE Hans Vesterdal, Elizabeth, N. 9., assignor to 7 Standard Oil Development Company, a corporation of Delaware No Drawing. Original application September 7,

1946, Serial No. 695,564. Divided and this application July 12, 194}, Serial No. 760,691

1 This application is a division of my prior application Serial No. 695,564, filed September '7, 1946. The present invention relates to improvements in the art of synthesizing hydrocarbons and more particularly it relates to catalysts which are particularly suitable for this reaction.

The synthesis of hydrocarbons from carbon monoxide and hydrogen is a matter of record and to some extent in certain countries, such as Germany, gasoline and other normally liquid hydrocarbons have been prepared commercially in this manner. Originally the synthesis of hydrocarbons from carbon monoxide and hydrogen was accomplished in the presence of a cobalt catalyst usually supported on a material such as kieselguhr and promoted with a material such as thoria. This synthesis, usually carried out at around 400 F., resulted in the production of straight-chain parafiinic compounds for the most part. Later a process was developed in which the catalyst was iron, and in which the temperature was substantially higher than in the first-mentioned process;

that is to say, it was somewhere between about 450 to 675" F. In this latter type of process where the iron catalyst was used, the process further difiered from the earlier one in that the ratio of hydrogen to carbon monoxide fed to the reaction zone was somewhat lower, being of the order of, say, 1 to 1 /2 mols of hydrogen per mol of carbon monoxide in the feed to the reaction. The product from the process employing the iron catalyst was different from that using the cobalt catalyst in that the former contained a substantial quantity of olefins and, therefore, the gasoline made using the iron catalyst usually possessed a higher octane number than produced in the cobalt catalyst process. a

There have been a number of proposals made by prior investigators for preparing a suitable iron type catalyst utilizable in the hydrocarbon syn thesis reaction. For example, it has heretofore been proposed that a suitable catalyst for the hydrocarbon synthesis may be made by roasting pyrites or a spent pyrites to convert the same to an iron oxide and then to reduce the iron oxide to metallic iron. Other proposals have included reducing a natural iron oxide, mineral or ore such as magnetite, hematite, limonite, etc. Still other proposals include'the use of those types of iron commonly employed in the synthetic ammonia process. Furthermore, certain promoters designed to increase the activity of the catalyst have been proposed heretofore. i

In a specific sense, my present invention relates 3 Claims. (01, 252. 433) in the hydrocarbon synthesis reaction by incorporating therein certain promoters. It is known that good catalysts for hydrocarbon synthesis areproduced by the addition of potassium compounds, such as K2003, KF, or K1204 to iron oxide followed by reduction in the temperature range 600 to 1600" F. I have now found that by combining fluoboric acid with a metal such as potassium or sodium to form metal fiuoborates, superior promoters for iron catalysts are formed.

'Although NaBF4 may be used as promoter, I

prefer the potassium fluoborate KBFi. The promoter may be added to pure iron oxide or hydroxide or to iron ores such as magnetite, hematite, limo'nite, etc., in amounts varying between about 0.2 and 10.0% based on the iron present.

Various procedures maybe employed for the addition of the promoter to the iron base. Thus the base may be moistened with an aqueous solution of the promoter at room' temperature followed by evaporation of the water, or the aqueous solution, or even the molten promoter itself may be. sprayed into the zone containing the iron base. This method may also be employed for reacti vation of partly spent catalyst. The iron base may be reduced with hydrogen or other reducing gases either before-or after addition of the promoter. Reduction temperatures may bevaried between about 500 and 1600 F. When reducing the catalyst after adding the promoter, however, the temperatures should preferably not exceed the melting point of the promoter, so that when using KBF-i, the reduction' temperature should preferably be held below 986 F. and with NaBF; below about 720 F.

Other fiuoborates such as calcium and caesium fiuoborates may also be used as promoters for the iron catalysts. Also mixtures of fiuoborates may be used. After reduction these catalysts may be used either in fixed bed, fluid catalyst, or movingbecltypes of operation.

The main object of my invention, therefore, is to prepare a catalyst comprising iron which is adapted not only to promote the reaction between carbon monoxide and hydrogen to form hydrocarbons and oxygenated hydrocarbons, but also to promote to a greater degree than catalystsheretofore employed, the polymerization of olefins so that normally gaseous olefins existing in a nascent state will be polymerized or condensed to olefinic hydrocarbons boiling in the gasoline boiling range.

Other and further objects of this invention will appear fromthe following more detailed deto improving the activity of an iron. catalyst fifi scription and claims.

. ysis of the extracted catalyst.

anareo 3 To illustrate my invention I set several specific examples:

Example 1 9.11 grams of potassium fluoborate (KBF4) were dissolved in 225 cc. of hot distilled water. The solution was poured onto 491 grams powdered iron oxide (or commercial pigment: red iron oxide) while mixing to form a paste. The paste was dried at 220 FL, then pilled in the presence of a 2 per cent of a hydrogenated vegetable oil (Sterotex) which was used as a lubricant for the pilling operation. The Sterotex was burned from the pills by heating in air at 850 F.

forth below for 3 hours. On reducing the pills for 4 hours at 900 F. with hydrogen at atmospheric pressure (1000 volumes H2 per volume of catalyst per hour) the catalyst'was ready for synthesis operation.

Example 2 Example 3 The same as in Example 2 except that the reduction temperature was 700 F., the hydrogen pressure 300 pounds per square inch and the linear velocity 0.5 ft. per second.

Example 4 The same as in Example 3 except that the promoter was NaBF; instead of KBF Example 5 The catalyst prepared in Example 1 was used in a test for production of hydrocarbons from carbon monoxide and hydrogen. Fifty cubic centimeters of the catalyst pills were placed in a reactor surrounded by a jacket containing a heat exchange fluid for temperature control. Synthesis gas in which 0.92 mol of hydrogen were present per mol of carbon monoxide was passed,

through the catalyst bed at 250 pounds per square inch gauge pressure at a flow rate of 200 volumes of gas (STP) per volume of catalyst per hour while adjusting the temperature to give about 95, per cent conversion of carbon monoxide. Under these conditions a yield of liquid hydrocarbons (C4+) of 211 cc. per cubic meter of carbon monoxide plus hydrogen consumed were obtained when operating at 550 F. with a carbon monoxide conversion of 96.4 per cent. Including the propane and propylene produced, the yield increased to 254 cc. per'cubic meter of CO-l-H: consumed. The product water produced at the same time amounted to 53.7 cc. per cubic meter of CO+H2 consumed and contained about 14.5 weight per cent alcohols and 3.7 weight per cent acids calculated as ethyl alcohol and acetic acid, respectively. After operation for 258 hours at 500 to 599 F., the catalyst was extracted with benzene followed by carbon and hydrogen anal- The wax .extracted amounted to 13.2 weight per cent on the extracted catalyst while the carbon and hydrogen of the non-extracted or residual contaminants saturated, as indicated by an olefin content of were 2.48 per cent and 0.18 per cent, respectively. Assuming a hydrogen to carbon ratio of 15 to 85 in the residual wax, the amount of wax left on the catalyst amounted to 1.2 per cent, corresponding to about 1.0 per cent carbon. The carbon on the catalyst on a wax-free basis was, therefore, 2.48 per cent minus 1.0 per cent, equaling 1.48 per cent, and the wax content 13.2 plus 1.2, equaling 14.4 per cen p The. catalyst was quite stable as indicated by a conversion of 95.3 per cent at 539 F. in hours 102 to 147 of the run, as compared to 96.4 per cent conversion at 549 F. in hours 213 to 258.

The hydrocarbon product produced was un- 80.8 weight per cent cent in the C5 cut.

In the following table the KBF4 promoted catalyst is compared with F8203 promoted with KF and with KzCOa.

Hydrocarbon synthesis [0.8 to 1.0 mm 112 00, 200 v. v./hr., 25o p.'s. i. g. Catalysts reduced with H, (100 v./v./hr.) for 4 hours at 900 F. before the tests.]

in the C4 cut, and 85.3 per 1 Percentages are on a weight basis.

I Reduced at 900 F. followed by sintering in H; at 1200 4 hours to reduce carbon formation The above data show that KBF4 is a true promoter for in two comparative runs, one using the KBF4 and the other KF, it will be noted that the yield of liquid product containing C4+ hydrocarbons was approximately the same in both runs even though the run in which the KBF4 was used was conducted at a temperature 91 degrees below that employed in the run using KF. However, the important advantage of KBF4 over KF' will be noted in the formation of carbon in the two runs. Thus, in the case of the KBF4 promoted catalyst 0.59 weight per cent carbon was formed on the catalyst per 100 hours of the run while in the KF promoted catalyst 2.36 weight per cent carbon was formed on the catalyst per 100 hours of the run. Kl? is a commonly used promoter and one of the best prior to my invention. However, all the known promoters had the defect that the runs in which they were used produced an inordinate amount F for of carbonaceous deposits on the catalyst and in a fluid system this is highly undesirable since carbonaceous deposits on the catalyst not only lower its activity but cause physical disintegration of the catalyst to the extent that it cannot be fluidized in a dense, turbulent, ebullient mass of catalyst but rather tends to pass out of the reactor at the top thereof with the product vapors. As is known, in the bottom drawoif type of operation it is highly desirable that the main bulk of catalyst be separated from the vapors in the upper portion of the reactor and remain therein while the product vapors issue from the reactor substantially freed of catalyst and containing merely traces of fines. As stated, however, when the catalyst is highly carbonized, it is impossible to achieve this result; hence the importance of minimizing the amount of carbon formed on the catalyst during the operation.

a 5 Numerous modifications o! my invention may bemadebythosewhoaretamiliarwiththisart without departing from the spirit thereof.

What is claimed is: 1. The method of forming an iron-containing catalyst suitable for use in promoting the synthesis oi hydrocarbons from carbon monoxide thereatterreducing at least a part of the iron oxide to the metallic state. v

2. The method set forth in' claim 1 in which potassium fluoborate is incorporated into the iron and hydrogen, which comprises incorporating an alkali metal fluoborate into iron oxide in amounts such that the catalyst contains from 0.2 to 10 weight per cent alkali metal fluoborates and oxide catalyst.

3. The method of claim 1 in which the iron oxide is reduced ata temperature within the range of from about 600 to 1600 F.

l HANS G..VESTERDAL.

No references cited. 

